Impairment of memory organization in patients with schizophrenia or schizotypal disorder

Atypical semantic cognition in schizotypal personality disorder and borderline personality disorder

Increased schizotypal traits have previously been associated with atypical semantic cognition in community samples. However, no study has yet examined whether adults diagnosed with schizotypal personality disorder (SPD) display atypical semantic fluency and memory. We hypothesized that 24 adults diagnosed with SPD would name more idiosyncratic words on the semantic fluency task and show decreased semantic recall for animal and fruit category words compared with 29 participants with borderline personality disorder (BPD) and a community sample of 96 age-matched controls. We examined whether atypical semantic cognition was specifically associated with disorganized and eccentric speech and thinking, or more broadly with pathological personality traits and personality functioning. Our main hypothesis was confirmed, as the SPD participants named more idiosyncratic words and recalled fewer semantically related words compared with controls. Surprisingly, participants with BPD likewise named more atypical words compared with controls. More idiosyncratic semantic fluency was associated with more eccentric speech and thinking. Increased idiosyncratic semantic fluency and reduced semantic recall were both coupled to increased detachment and lowered personality functioning, while reduced semantic recall further was related to increased interpersonal problems. Our findings suggest that persons with SPD, and to a lesser degree BPD, show atypical semantic cognition, which is associated with eccentric speech and thinking, and more broadly with impaired personality function, social withdrawal, and emotional flatness. The idiosyncratic semantic cognition may worsen difficulties with social reciprocity seen in SPD and BPD.

The relationship between cognitive reserve focused on leisure experiences and cognitive functions in bipolar patients

Bipolar disorder (BP) is characterized by cognitive decline. Individual differences exist in maintaining cognitive function due to daily physical activity and sleep. We examined the relationship between leisure experiences as proxies for cognitive reserve (CR) and cognitive function in patients with bipolar disorder after adjusting for daily physical activity and sleep. The CR of patients with BP (n = 24) and healthy study controls (HC) (n = 24) was assessed using premorbid IQ, years of education, and leisure activity history. Performance-based neuropsychological tests were performed to evaluate cognitive function. A self-reported scale was used to assess resilience. Physical activity and sleep were measured using an activity meter. Verbal fluency, story memory, and verbal memory were significantly positively correlated with the kinds of leisure experiences in patients with BP. A hierarchical regression analysis accounting for confounding factors showed that verbal fluency and memory were associated with the kinds of leisure experiences. Neither years of education nor resilience were significantly associated with neuropsychological scores. Various leisure experiences in patients with BP are associated with higher language-related cognitive functioning. Engaging in various leisure experiences may affect higher cognitive functions related to language.

Premorbid intellectual ability in schizophrenia influence family appraisal related to cognitive impairments: a cross-sectional study on cognitive impairment and family assessments

BACKGROUND

Patients with schizophrenia are unaware of their cognitive impairments. Misperception of cognitive impairment is an important factor associated with real-world functional outcomes in patients with schizophrenia. The patient's family member plays a crucial role in detecting patients' cognitive impairments when the patients are unaware of their own cognitive impairments. Previous studies have reported that not only the patient's subjective rating, but also the patient's family members' rating of their cognitive impairment may not be precise. However, it is unclear why family ratings are inaccurate, and which factors impact family ratings. This study investigated whether family ratings differed significantly from the patients' subjective ratings of the patients' cognitive impairments and sought to determine the reason for the differences between the family ratings and the patients' neurocognitive performances. We investigated the relationship between patients' subjective ratings, family ratings for patients' cognitive impairments, neuropsychological performance, and other aspects, including premorbid IQ and clinical symptoms.

METHOD

We evaluated 44 patients with schizophrenia for cognitive function using neuropsychological tests; in addition, both the patients and their families rated the patients' cognitive impairments through questionnaires. We used the Mann-Whitney U test to examine whether the family ratings differed significantly from the patients' self-reported ratings of their cognitive impairment. We conducted multiple regression analysis and structural equation modeling to determine why the patients' subjective ratings and the family ratings were not definitively associated with the patients' neurocognitive performances. We performed multiple regression analysis with a stepwise method with neurocognitive performance, premorbid IQ, positive symptoms, and negative symptoms as independent variables and family ratings of patients' cognitive impairments as dependent variables.

RESULTS

We found that the family ratings differed significantly from the patients' subjective self-reported ratings of their cognitive impairments. Our results showed that the premorbid IQ of patients is the strongest predictor of family ratings. Furthermore, among the neurocognitive domains, only the processing speed of patients was associated with family ratings.

CONCLUSIONS

We found that the family ratings were not consistent with the patients' subjective self-reported ratings and the family ratings were most affected by the patients' premorbid intellectual abilities. These results suggest that the families' current assessments of the patients' current cognitive impairments were affected by the patients' premorbid intellectual ability rather than the patients' current neurocognitive performance. Patients' processing speed predicted family ratings; however, family members' ratings were not related to verbal learning/memory, executive function, and language of patients. Therefore, our findings highlight that patients' family ratings may differ from patients' subjective ratings, results of performance-based neuropsychological tests, and clinician ratings.

Subjective organization in the episodic memory of individuals with Parkinson's disease associated with mild cognitive impairment

Word clustering (i.e., the ability to reproduce the same word pairs in consecutive recall trials of an unrelated word list) has been extensively investigated as a proxy of subjective organization (SO) of memorandum. In healthy subjects and in groups of brain-damaged patients, the rate of SO generally predicts accuracy of word list recall. This study aimed at evaluating SO in the performance of patients with Parkinson's disease (PD) on a word list recall task in order to investigate the basic mechanisms of episodic memory impairment that are frequently observed in these patients. For this purpose, 56 PD patients, who were stratified according to the presence and quality of mild cognitive impairment (MCI), and a group of healthy controls (HCs) were administered a word list task and an extensive battery of neuropsychological tests. Results showed that recall accuracy on the word list task progressively decreased passing from HC to PD patients without cognitive impairment, to patients with single-domain dysexecutive MCI and to patients with multiple-domain dysexecutive and amnesic MCI. Conversely, only the latter PD group showed a lower SO score than that achieved by the other groups. In the overall PD group, correlational and regression analyses demonstrated that SO scores and a composite score of executive functions were not reciprocally related, but both provided an independent and significant contribution to the prediction of word list recall accuracy. These data are discussed in terms of the contribution of executive functions and hippocampal storage processes to the onset of memory impairment in PD.

Sex differences in verbal and nonverbal learning before and after temporal lobe epilepsy surgery

Women outperform men in a host of episodic memory tasks, yet the neuroanatomical basis for this effect is unclear. It has been suggested that the anterior temporal lobe might be especially relevant for sex differences in memory. In the current study, we investigated whether temporal lobe epilepsy (TLE) has an influence on sex effects in learning and memory and whether women and men with TLE differ in their risk for memory deficits after epilepsy surgery. 177 patients (53 women and 41 men with left TLE, 42 women and 41 men with right TLE) were neuropsychologically tested before and one year after temporal lobe resection. We found that women with TLE had better verbal, but not figural, memory than men with TLE. The female advantage in verbal memory was not affected by temporal lobe resection. The same pattern of results was found in a more homogeneous subsample of 84 patients with only hippocampal sclerosis who were seizure-free after surgery. Our findings challenge the concept that the anterior temporal lobe plays a central role in the verbal memory advantage for women.

Neuropsychological Characteristics and Their Association with Higher-Level Functional Capacity in Parkinson's Disease

BACKGROUND/AIMS

Little is known about the relationship between cognitive functions and higher-level functional capacity (e.g. intellectual activity, social role, and social participation) in Parkinson's disease (PD). The purpose of this study was to clarify neuropsychological characteristics and their association with higher-level functional capacity in PD patients.

METHODS

Participants were 31 PD patients and 23 demographically matched healthy controls. Neuropsychological tests were conducted. One year later, a questionnaire survey evaluated higher-level functional capacity in daily living.

RESULTS

The PD group scored significantly lower than the control group in all cognitive domains, particularly executive function and processing. Executive function, processing speed, language, and memory were significantly correlated with higher-level functional capacity in PD patients. Stepwise regression showed that only executive function (Trail Making Test-B), together with disease severity (HY stage), predicted the higher-level functional capacity.

CONCLUSION

Our findings provide evidence of a relationship between executive function and higher-level functional capacity in patients with PD.

Does sleep improve memory organization?

Sleep can integrate information into existing memory networks, look for common patterns and distil overarching rules, or simply stabilize and strengthen the memory exactly as it was learned. Recent research has shown that sleep facilitates abstraction of gist information as well as integration across multiple memories, insight into hidden solutions, and even the ability to make creative connections between distantly related ideas and concepts. To investigate the effect of sleep on memory organization, 35 normal volunteers were randomly assigned either to the sleep (n = 17) or wake group (n = 18). The sleep subjects performed the Japanese Verbal Learning Test (JVLT), a measure of learning and memory, three times in the evening, and slept. On the following morning (9 h later), they were asked to recall the words on the list. The wake subjects took the same test in the morning, and were asked to recall the words in the same time interval as in the sleep group. The semantic clustering ratio (SCR), divided by the total number of words recalled, was used as an index of memory organization. Our main interest was whether the sleep subjects elicit a greater increase in this measure from the third to the fourth assessments. Time × Group interaction effect on SCR was not significant between the sleep group and wake group as a whole. Meanwhile, the change in the SCR between the third and fourth trials was negatively correlated with duration of nocturnal waking in the sleep group, but not other sleep indices. Based on this observation, further analysis was conducted for subjects in the sleep group who awoke nocturnally for <60 min for comparison with the wake group. A significant Time × Group interaction was noted; these "good-sleepers" showed a significantly greater improvement in the memory index compared with the wake subjects. These results provide the first suggestion that sleep may enhance memory organization, which requires further study.

The relationship of verbal learning and verbal fluency with written story production: implications for social functioning in first episode psychosis

BACKGROUND

Impairments in speech, communication and Theory of Mind are common in schizophrenia, and compromise social functioning. Some of these impairments may already be present pre-morbidly. This study aimed to investigate verbal functions in relation to written story production and social functioning in people experiencing a first episode of psychosis (FEP).

METHOD

Two groups of participants: FEP (N=31) and healthy controls (HC, N=31), completed measures of clinical status, social functioning, a series of neuropsychological tests targeting verbal functioning, and the "Frog Where Are You?" story production task.

RESULTS

Story results showed reduced efficiency (words per minute) and self-monitoring (corrections per minute) for FEP compared with HC groups (p<0.01). The FEP group performed significantly poorer than the HC group on most indices of verbal learning and verbal fluency. Story production was positively associated with verbal learning and verbal fluency for the FEP group only (p<0.05). Premorbid function decline was associated with impaired verbal learning and memory for the FEP group.

CONCLUSION

Individuals with FEP show a childhood history of reduced social and academic performance that is associated with skills essential for daily social interactions, as evidenced by the findings for story production, verbal learning and verbal fluency.

Depth-of-processing effects on semantic activation deficits in schizophrenia: an electrophysiological investigation

N400, an event-related brain potential (ERP) waveform elicited by meaningful stimuli, is normally reduced (made less negative) by relatedness between the eliciting stimulus and preceding ones (N400 semantic priming). Schizophrenia patients' N400 semantic priming deficits suggest impairment in using meaningful context to activate related concepts in semantic memory. We aimed to examine the degree to which this impairment can be ameliorated by task instructions that more explicitly require processing of stimulus meaning. We recorded ERPs from 16 schizophrenia patients and 16 controls who viewed prime words each followed at 750-ms stimulus-onset asynchrony by an unrelated or related target word, or a nonword, in a non-semantic task (indicating whether a letter occurred in the target) compared to an explicit semantic task (judging prime-target relatedness). Consistent with previous work, controls exhibited greater N400 semantic priming (larger amplitude reductions for related versus unrelated targets) in the semantic task than in the orthographic task. Schizophrenia patients showed this same pattern, although their N400 semantic priming effects were smaller than controls' across tasks. Nevertheless, patients' priming effects increased as much as did controls' from the orthographic to the semantic task. Thus, connections among related concepts in schizophrenia patients' semantic memory appear grossly intact, such that, given a meaningful stimulus, they can make use of explicit cues to activate related concepts at a neurophysiological level, although their ability to do so remains less than normal. These data provide support for further research on semantic-cueing strategies for cognitive remediation of verbal memory in schizophrenia.

Effect of explicit instruction on Japanese Verbal Learning Test in schizophrenia patients

After random assignment of 20 schizophrenia patients to either an explicit or normal instruction group, the Japanese Verbal Learning Test was administered to them. Results reveal that explicit instruction group patients demonstrated more improved memory performance using semantic clustering, suggesting that explicit and direct teaching facilitates patients' learning of information.

Individual Differences in Episodic Memory: The Role of Self-initiated Encoding Strategies

Individuals' abilities to form and retrieve episodic memories vary widely. Consistent with this, there are substantial individual differences in brain activity during encoding and retrieval that are associated with individual differences in memory performance. Growing evidence suggests that individual differences in self-initiated encoding strategy use play an important role in individual differences in episodic memory and brain activity during intentional encoding. This review examines the role of individual differences in self-initiated encoding strategy use in individual differences in episodic memory, and outlines the major findings of brain lesion and functional neuroimaging studies that characterize the neural correlates of individual differences in self-initiated encoding strategy use. The relevance of individual differences in self-initiated encoding strategy use to understanding episodic memory impairments and alterations in brain activity in clinical populations such as individuals with schizophrenia is also discussed.

The relationship between prefrontal brain volume and characteristics of memory strategy in schizophrenia spectrum disorders

The present study investigated the relationship between memory strategy use and prefrontal gray/white matter volumes of healthy control subjects, patients with schizophrenia or schizotypal disorder. Gray/white matter volumes were measured for the superior, middle, inferior, ventral medial and orbital prefrontal regions, using high-resolution magnetic resonance (MR) images that were acquired from 35 patients with schizophrenia, 25 patients with schizotypal disorder and 19 healthy subjects. Participants were also administered the Japanese Verbal Learning Test (JVLT). In control subjects, larger left inferior frontal and straight gyrus's gray matter volumes were associated with higher semantic clustering rates on the JVLT, and smaller left inferior frontal gray matter volumes were associated with higher serial clustering ratio. In schizophrenic patients, smaller left orbitofrontal gray matter volumes were associated with lower semantic clustering rates on the JVLT. In schizotypal patients, smaller left inferior frontal white matter volume was associated with smaller serial clustering rates and larger semantic clustering rate. These findings suggest that semantic organization in schizophrenic patients might depend on mobilization of a memory strategy that is mediated by orbitofrontal cortex functioning. Failure to use a semantic organization strategy might be related to reduced volume in the inferior frontal gyrus. The findings for schizotypal patients suggest a compensation mechanism to remember the words using a serial processing strategy is at work when the inferior frontal gyrus cannot mediate semantic processing.

Seeing is remembering: do deficits in closure affect visual memory recognition in schizophrenia?

INTRODUCTION

Episodic memory is significantly impaired in people with schizophrenia. The precise cause of this impairment has yet to be determined, as the formation of episodic memories is dependent on other processes, some of which also show impairment in schizophrenia. One such process is closure, that is, the filling-in of missing information. Failure to close adequately incomplete stimuli may cause people with schizophrenia to store inadequate or piecemeal representations in memory.

METHODS

Forty people with schizophrenia and 21 healthy comparison subjects participated in the study. The experiment was divided into six blocks, each of which involved both an encoding and a recognition phase. During the encoding phase, 20 figures were presented sequentially and participants had to determine whether each was symmetric or asymmetric. These figures were either complete or fragmented at three different levels. In subsequent recognition phase, 40 abstract figures (20 new and 20 old) were presented. All figures were complete in this phase.

RESULTS

Memory performance of both groups was affected similarly by fragmentation, with an additional increase in performance afforded by a slight fragmentation for participants with schizophrenia.

CONCLUSION

Slight fragmentation may have induced a perceptual difficulty that was mild enough to increase visual processing without compromising it. Closure was thus not involved in the episodic memory deficit of people with schizophrenia.

Disrupted integrity of the fornix is associated with impaired memory organization in schizophrenia

BACKGROUND

The fornix is a major projection of the hippocampus to and from other brain regions. A previous diffusion tensor imaging (DTI) study has reported disrupted integrity of the fornix in patients with schizophrenia. However, functional significance of the DTI abnormalities of the fornix in schizophrenia has not been fully studied yet. We investigated an association between DTI abnormalities of the fornix and impairment of memory organization in schizophrenia.

METHODS

Thirty-one patients with schizophrenia and 65 age- and gender-matched healthy controls underwent DTI, and fractional anisotropy (FA) and mean diffusivity (MD) were measured in cross-sections of fornix tractography. In addition, all of the patients and 32 controls performed a verbal learning task specialized for evaluating memory organization, the verbal memory subscale of the Wechsler Memory Scale-Revised, the category- and letter fluency tests, and the Japanese version of National Adult Reading Test.

RESULTS

Statistically significant reduction of FA and increase of MD were found in the fornix of patients with schizophrenia compared with controls with no significant lateralization. A significant patients-specific correlation was found between increased MD in the left fornix and lower scores on utilization of semantic organization in the verbal learning task. In addition, increased MD in the right fornix showed a patients-specific association with poorer performance on the category fluency test, which indexes organization of long-term semantic memory. These patients-specific correlations, however, were not statistically lateralized to either hemisphere.

CONCLUSIONS

These results indicate that disrupted integrity of the fornix contributes to impaired memory organization in schizophrenia.

Cognitive functioning related to quality of life in schizophrenia

The present study compared the cognitive function of patients with schizophrenia to that of healthy subjects, and investigated the relationships between cognitive function and quality of life (QOL). Participants consisted of 53 patients meeting DSM-IV criteria for schizophrenia and 31 normal controls. All participants completed a neuropsychological test battery assessing executive function, verbal memory, and social knowledge. QOL was rated using the Schizophrenia Quality of Life Scale. Patients with schizophrenia showed lower performance across various cognitive measures of memory, including the Sentence Memory Test, the Verbal Learning Test, and the Script Test, as well as the Rule Shift Cards Test of executive function. Multiple regression analyses were used to evaluate the neuropsychological measures and clinical symptoms to predict QOL. The QOL total score, the social initiative score or the empathy score were significantly predicted by the Script or/and the Sentence Memory. Neuropsychological functioning was unrelated to most QOL scores in the presence of clinical symptoms, while ability of empathy in the QOL was predicted by performance of the Sentence Memory Test. These results demonstrated patients with schizophrenia have deficits in executive function, memory and learning, and social knowledge, and that social knowledge and memory are related to QOL. Thus, in patients with schizophrenia, deficits in social knowledge appear to be associated with current QOL in general, and specifically with the capacity for empathy and social initiative.

Impairment of story memory organization in patients with schizophrenia

The aim of the present paper was to examine the organization of story memory in schizophrenia. Participants were 35 patients with schizophrenia and 24 healthy subjects who completed the Wechsler Memory Scale-Revised. The organization of story memory was evaluated with the Logical Memory subtest. Schizophrenia patients scored significantly lower than controls on thematic sequencing, and significant negative correlations were found between positive symptoms and thematic sequencing. These findings suggest that schizophrenia has deficits in organization of story memory, which are related to symptoms such as disorganized thoughts and behavior.

Activation of the prefrontal cortex during memory learning: near-infrared spectroscopy study

Near-infrared spectroscopy (NIRS) is an optical method to determine oxygenated and deoxygenated hemoglobin concentration changes in the human cerebral cortex. The purpose of this study was to examine the hemodynamic response of the prefrontal area during words memory learning using NIRS. A total of 23 healthy subjects participated in the present study. Hemodynamic response in the prefrontal cortex was measured using a NIRS system. The number of words recalled and stimulus category repetition (SCR) were analyzed by the words memory learning task. During the words memory learning task, oxygenated hemoglobin concentrations increased and deoxygenated hemoglobin concentrations decreased. This typical pattern was maintained during each memory stage, but the degree of change of [oxyHb] during encoding from the first condition to the second condition was significantly larger than that during retrieval. This suggests that memory organization is facilitated during encoding of the first condition, and that the retrieval period through two conditions still involves more activation in the prefrontal area than the encoding period. An increase of [oxyHb] was not recognized and activation was inhibited when the strategy was applied. Subjects produced more SCR in the second condition than in the first condition in spite of strategy instruction. This result suggests healthy people can find out implicit category by themselves following learning even without instruction. There were no significant relationships between the behavior indices and the changes in hemoglobin. Further studies are needed to clarify usefulness of NIRS in patients with psychiatric disorder.